Colicin El has recently been shown by ourselves to deenergize the cell membrane with respect to active transport in a time very similar to that necessary for adsorption of the protein to the cell receptors, and significantly faster than previously thought for the depolarizing effect of colicin El. The mechanism for this rapid deenergization is being sought. A preparation of colicin E2 has been developed with much higher specific activity than any others in the literature. Effort is being directed at present toward the stablization of this high activity preparation.